JP3905669B2 - Power steering device - Google Patents

Description

【００４５】
ここで、この表１では閉を「×」で示す。
また、▲１▼〜▲６▼のそれぞれの動作状態において、圧力流体の流れを確保したり遮断したりする各連通部Ａ〜Ｆでの状態のうち、重要な部分を太字で示す。
【００４６】
上述した表１の▲１▼および図４から明らかなように、スプールバルブ２０は、メインポンプＰ１が正常に駆動して圧力流体を吐出しているときには、連通部Ａ、Ｃ、Ｄ、Ｆが開となり、それ以外は閉となっている。
したがって、この状態では、メインポンプＰ１から圧力流体が給送されるとともに戻り側がメインタンクＴ１に還流するようになっており、舵取ハンドルの操作に伴ってコントロールバルブ１０によってパワーシリンダ３が適宜作動し、所要の状態での操舵補助力を得ることができるのである。しかも、このときには図４において連通部ＡとＤとが開となっていて、サブポンプＰ２とサブタンクＴ２とは短絡しており、無負荷状態であるから、動力損失が低減される。
【００４７】
上述した通常状態において、メインポンプＰ１からの圧力流体の流量が少なくなり、室３５に作用しているパイロット圧が低下すると、スプール３２は図４の状態から図５の状態になるように図中右側に移動する。
これらの状態を表１の▲２▼〜▲４▼に基づいて説明すると、メインポンプＰ１から連通部Ｃを介しての供給が減少するとともに、連通部Ｂが徐々に開いてサブポンプＰ２からの圧力流体の給送が開始される。なお、上述した▲２▼の状態は瞬時であって、▲１▼から▲２▼を経て直ぐに▲３▼の状態に以降する。
【００４８】
このときには、両ポンプＰ１，Ｐ２からの圧力流体が合流して流れる時点を含んでメインポンプＰ１からサブポンプＰ２に切換わる。
なお、この状態では、サブポンプＰ２とサブタンクＴ２との短絡状態は連通部ＡとＤが徐々に閉じることにより解除されることになる。
【００４９】
また、表１の▲４▼〜▲６▼に示すように、パワーシリンダ３からの戻り流体は、メインタンクＴ１への還流路から両タンクＴ１，Ｔ２への合流した還流路を経て、サブタンクＴ２への還流路へと切換わることになる。
【００５０】
このような戻り側においても、両タンクＴ１，Ｔ２への戻り状態を通過してからメインとサブとの切換えが行われるから、戻り側の流通量を必要かつ充分に確保できるから、パワーシリンダ３側での作動に支障をきたすことはない。
ここで、上述した▲５▼の状態は連通路Ｆを閉じる過程で戻り側の流路を確保するためのものであって、▲４▼から▲６▼への切換りも瞬時に行われる。
また、図３および図５に示す状態では、メインポンプＰ１側の供給路やメインタンクＴ１への還流路は完全に閉塞されるとともに、サブポンプＰ２からの供給路とサブタンクＴ２への還流路とが確保されている。
【００５１】
以上のような動力舵取装置１のメイン、サブのポンプＰ１、Ｐ２の切換えを行うスプールバルブ２０においては、メインポンプＰ１側の圧力流体の流体圧をパイロット圧として作動させる際に、スプール３２の動きに伴ってメイン、サブを単純に切換えるのではなく、その切換え途中でメインポンプＰ１とサブポンプＰ２、メインタンクＴ１とサブタンクＴ２がそれぞれ同時にコントロールバルブ１０のポンプポートＰ、タンクポートＴに連通する状態を設けている。したがって、スプールバルブ２０の切換え途中での圧力流体の給送量や戻り量が不足したりすることがなく、ポンプＰ１、Ｐ２、タンクＴ１、Ｔ２とパワーシリンダ３との間で所要の供給量、戻り量を得て、パワーシリンダ３による操舵補助力を適切に生じさせることができるのである。
【００５２】
換言すると、本発明によれば、上述した切換え用のスプールバルブ２０を用いることにより、常時はメインポンプＰ１からの圧力流体の給送によってコントロールバルブ１０を介してパワーシリンダ３のいずれかのシリンダ室８ａ，８ｂに圧力流体が供給され、他方の室がメインタンクＴ１に接続され、所要の操舵補助力を得て舵取操作を容易に行うことができる。
また、万一、メインポンプＰ１からの圧力流体の流量が低下すると、その状態をパイロット圧の低下によって切換え用スプールバルブ２０が作動して給送系、還流系の切換えを行い、サブポンプＰ２からの圧力流体によって操舵を容易に行うことができる。
【００５３】
なお、本発明は上述した実施の形態で説明した構造には限定されず、各部の形状、構造等を適宜変形、変更し得ることはいうまでもない。
たとえば操舵輪を転舵するための動力舵取装置のパワーステアリング本体部１を作動させる油圧源として、自動車用エンジンによって駆動されるポンプをメインポンプＰ１を用い、補助用の油圧源としてたとえば自動車の車軸または電動モータの回転によって駆動されるポンプをサブポンプＰ２を用いた場合を説明したが、本発明はこれに限らない。たとえばメインポンプＰ１とサブポンプＰ２とを共に電動モータで駆動するタイプにしてもよい。
【００５４】
勿論、サブポンプＰ２としては、上述したような車軸駆動方式や電動モータなどによる電動駆動式のものに限らず、エンジン以外の適宜の駆動源で駆動できるものであればよい。
また、上述した実施の形態では、圧力流体の戻り側にメインタンクＴ１とサブタンクＴ２を別々に設けた場合を説明したが、これらを共通のタンクによって構成することもできる。
【００５５】
また、上述した実施の形態では、パワーステアリング本体部１をボールねじ式である場合を説明したが、本発明はこれに限らず、ラックピニオン式やその他のタイプのパワーステアリング構造のものであってもよい。
【００５６】
【発明の効果】
以上説明したように本発明に係る動力舵取装置によれば、メイン、サブ切換え用のスプールバルブによって常時はメインポンプのみをコントロールバルブに接続し、このメインポンプからの圧力流体を流路切換え用コントロールバルブを介してパワーシリンダに給送し、所要の操舵補力を生じさせることができるから、舵取ハンドルの舵取操作に伴った操舵輪の所要状態での転舵を行える。しかも、このとき、サブポンプはタンク側に接続されており、無負荷状態で運転されているから動力損失は生じない。
【００５７】
また、本発明によれば、従来の装置のようにメインポンプからの圧力流体を絞り部を介して供給したり、サブポンプからの圧力流体を逆止弁を介して供給するようなことがないから、切換えバルブの存在が動力損失の原因となるようなこともない。
【００５８】
また、本発明によれば、たとえばエンジン駆動式のメインポンプが故障したり、このポンプからの圧力流体給送用配管等が損傷したりしたときには、このメインポンプの圧力流体をパイロット圧とするスプールバルブが瞬時に切換えられて、サブポンプをコントロールバルブに接続し、このサブポンプからの圧力流体をコントロールバルブを介してパワーシリンダに給送できるから、所要の操舵補助力をもって左、右操舵輪を転舵することができる。
【００５９】
したがって、本発明によれば、メイン、サブという二台のポンプとその給送系を切換えるスプールバルブとによって、車輌のエンジン駆動式のポンプが故障等で停止したりポンプからの圧力流体の供給配管が損傷したりしたときにも、左、右操舵輪の転舵を可能にし、しかも装置の構成部品数が少なく構造も簡単で小型化やコスト低減を装置構造であるにもかかわらず、無駄な消費馬力もなく、少流量化による燃費の向上を図ることができる。
【００６０】
また、本発明によれば、スプールバルブが切換え作動する際、たとえばメインポンプからサブポンプに切換えるにあたって、メインポンプおよびサブポンプの両方からの圧力流体を給送する状態を経てサブポンプからの圧力流体をコントロールバルブに給送する流路切換えを行ったり、コントロールバルブからの戻り流体をメインタンクおよびサブタンクの両方に還流させる状態を経てサブタンクに還流させる流路切換えを行う流路を備えているから、コントロールバルブを介してのパワーシリンダへの圧力流体の流量、戻り側流体の流路を常に必要かつ充分に確保しており、操舵輪を所要の状態で転舵させることができる。
【図面の簡単な説明】
【図１】 本発明に係る動力舵取装置の一つの実施の形態を示し、要部となる切換え用スプールバルブ部分を断面したパワーステアリング本体部の端面図である。
【図２】 図１におけるパワーステアリング本体部の側断面図である。
【図３】 図１の切換え用スプールバルブがメイン側からサブ側に切り換えられた状態を示すパワーステアリング本体部の端面図である。
【図４】 図１の要部となる切換え用スプールバルブを拡大した断面図である。
【図５】 図４の状態からスプールバルブが切換え作動し、上述した図３に相当する状態になったときの断面図である。
【符号の説明】
１…動力舵取装置のパワーステアリング本体部、２…入力軸（スタブシャフト）、３…パワーシリンダ、４…出力軸（セクタギヤ）、５…ステアリングボディ、６…バルブハウジング、７…ピストン、８ａ，８ｂ…左、右シリンダ室、１０…流路切換え用コントロールバルブ、１１…ウォームシャフト、１３…ロータ、１４…スリーブ、１６，１７…通路、２０…メイン、サブ切換え用スプールバルブ、２１…バルブボディ、２２，２３…第１、第２のポンプポート、２４，２５…第１、第２の戻りポート、２６，２７…通路、３１…バルブ孔、３２…スプール、３３…プラグ、３４…圧縮コイルばね（付勢手段）、３５…室、３６…パイロット通路、３７…室、３８…通路、５０…短絡通路、Ｐ１…メインポンプ、Ｐ２…サブポンプ、Ｔ１…メインタンク、Ｔ２…サブタンク。[0001]
BACKGROUND OF THE INVENTION
The present invention includes a power cylinder for turning left and right steering wheels (hereinafter referred to as steering wheels) in various vehicles including large vehicles such as large trailers and large trucks. The present invention relates to a power steering apparatus.
[0002]
[Prior art]
In this type of power steering apparatus, a spool for switching between two pressure fluid supply systems from each pump using a main pump and a sub pump as a fluid pressure source to a power cylinder that generates a steering assist force. For example, Japanese Patent Application Laid-Open No. 50-32374 discloses a structure having a switching valve having the following.
[0003]
In the initial state, this conventional switching valve is maintained in a state in which the pressure fluid from the main pump and the pressure fluid from the sub pump are supplied to the hydraulic pressure consumption unit (control valve or power cylinder). During normal operation when the fluid flow rate exceeds a certain level, only the pressure fluid from the main pump is fed by the spool valve that operates according to the fluid pressure difference before and after the throttle, and the sub pump is connected to the tank and short-circuited And the sub pump is operated in a no-load state.
[0004]
When the flow rate of the pressure fluid from the main pump decreases and falls below a certain amount, the operation of the hydraulic pressure consumption unit is enabled by the supply of the pressure fluid from the sub pump by the operation of the spool.
[0005]
In other words, this switching valve has a spool that operates according to the fluid pressure difference before and after the throttle portion provided in the supply passage of the pressurized fluid from the main pump, and when this spool is operated, the axial direction of the spool is changed. The connection path from the connection part of the pressure fluid from the sub pump provided in the part to the hydraulic pressure consumption part is closed.
[0006]
[Problems to be solved by the invention]
In the conventional power steering apparatus as described above, the spool for switching between the main pump and the sub pump is operated with the fluid pressure difference before and after the throttle portion provided in the supply passage of the pressure fluid from the main pump. It is inevitable that a power loss occurs when the pump is driven due to a pressure drop generated in the throttle portion.
[0007]
Further, in the above-described conventional apparatus, the pressure fluid from the sub pump or the pressure fluid from the main pump is joined to the pressure fluid supply path to the hydraulic pressure consumption section via the check valve when the spool is operated. Therefore, it is inevitable that power loss occurs due to a pressure drop when passing through the check valve.
[0008]
Further, in the above-described conventional apparatus, during the normal operation, the pressure fluid supply system from the sub pump is connected to the hydraulic pressure consumption unit until the pressure fluid from the main pump reaches a constant flow rate and the spool operates. It will be connected to a pressure fluid feed system. In this state, the sub-pump is operated in a loaded state, so that power loss occurs at this point.
[0009]
Further, in the above-described conventional example, the flow rate of the pressure fluid from the main pump is limited due to the restriction of the movement of the spool due to the structure that the supply passage is provided in the spool at the time of switching to return the valve spool. In some cases, the valve may not be restored even when the amount of air is insufficient. At this time, the flow of the pressure fluid from the main pump may be stopped.
[0010]
Furthermore, in the above-described conventional example, even if the supply flow rate from the main pump is insufficient, the pressure fluid from the sub pump may not be supplied depending on the operating state of the spool, and some measures that can eliminate such problems. It is hoped that
[0011]
The present invention has been made in view of such circumstances, and even when a vehicle engine-driven pump stops due to a failure or the pressure fluid supply piping from the pump is damaged, The right steering wheel can be steered, the number of component parts of the device is small, the structure is simple, the entire device can be downsized and the cost can be reduced, and there is no wasteful horsepower consumption. It aims at obtaining the power steering device which can aim at improvement of.
[0012]
[Means for Solving the Problems]
  In order to meet such an object, a power steering apparatus according to claim 1 of the present invention includes a main pump and a sub pump, a power cylinder that steers steering wheels by steering steering of a steering handle, and each pump. The flow path is selectively selected by a control valve for switching the flow path to be selectively supplied to the power cylinder, a main tank and a sub tank for storing hydraulic oil, and the pressure fluid supplied from the main pump. Main and sub switching spool valves, the flow path switching control valve and the main and sub switching spool valves are connected, and the pressure fluid from the main pump and sub pump is supplied from the main and sub switching spool valves. Pump port for supplying to the flow path switching control valve, and the flow path switching A control port and a main / sub switching spool valve, and a tank port for returning the return oil returned to the main tank and sub tank from the flow path switching control valve to the main / sub switching spool valve; The main and sub switching spool valve has a first position in which the pressure fluid from the main pump is supplied to the power cylinder and the pressure fluid from the sub pump is returned to the sub tank, and Pressure fluid from sub pumponlyOperates between the second position supplied to the power cylinder, and the main pump and the sub pump simultaneously communicate with the pump port during switching from the first position to the second position. It is characterized by the existence of a state.
[0013]
According to the present invention (the invention described in claim 1), during a normal operation in which an engine drive type main pump is operating, the pressure fluid from the main pump flows through the spool valve for main and sub switching. It is fed to the power cylinder from the path switching control valve. Accordingly, the left and right steered wheels are steered with the assistance of the required steering assist force.
[0014]
On the other hand, when the main pump fails or the pressure fluid supply piping from the pump is damaged, the main and sub switching spool valve connects the sub pump to the control valve, and the sub pump switches to the control valve. The pressure fluid to be fed is supplied to the power cylinder.
[0015]
A power steering apparatus according to a second aspect of the present invention is the power steering apparatus according to the first aspect, wherein a pilot pressure passage having a pressure fluid supplied from the main pump as a pilot pressure is connected to one end of a spool constituting the spool valve. The other end is provided with urging means for urging the spool toward one end.
[0016]
According to the present invention (the invention described in claim 2), when the pressure fluid is supplied from the main pump, the spool is moved to the other end side by the pilot pressure by the pressure fluid, and the energization is performed when the pressure fluid disappears. The spool is moved to one end side by the urging force of the means.
[0017]
A power steering apparatus according to a third aspect of the present invention is the short-circuit passage according to the first or second aspect, wherein the sub-pump is connected to the sub-tank during normal operation in the spool constituting the spool valve. Is provided.
[0018]
According to the present invention (the invention described in claim 3), when the flow rate of the pressure fluid from the main pump is sufficient, the sub pump is connected to the sub tank via the spool valve and is in a short circuit state, The sub-pump becomes unloaded.
[0019]
A power steering apparatus according to a fourth aspect of the present invention is the power steering apparatus according to the first or second aspect, wherein pressure fluid from the main pump is supplied to the control valve during normal operation to the spool constituting the spool valve. When the flow rate of the pressure fluid from the main pump decreases, the flow path for switching the flow path for supplying the pressure fluid from the sub pump to the control valve and the return fluid from the control valve during normal operation are A flow path for switching the flow path for returning to the sub tank when the flow rate of the pressure fluid from the main pump is reduced and returned to the main tank is provided.
[0020]
  According to the present invention (the invention described in claim 4), when the flow rate of the pressure fluid from the main pump decreases due to the movement of the spool of the spool valve for main and sub switching, the pressure fluid from the sub pump is joined and supplied. By feeding or supplying the pressure fluid from the sub pump, the supply flow rate to the power cylinder through the control valve is secured, and the return fluid from the control valve is sufficiently supplied to the main tank and the sub tank. By returning with the return flow path or returning to the sub-tank, a flow path for the return fluid from the power cylinder through the control valve is secured, and the steered wheels can be steered.
  A power steering apparatus according to a fifth aspect of the present invention is the power steering apparatus according to the first aspect, wherein the main and sub switching spool valve is in the middle of switching from the first position to the second position. The main tank and the sub tank are connected to the tank port at the same time.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
1 to 5 show an embodiment of a power steering apparatus according to the present invention.
In these drawings, what is indicated by reference numeral 1 in FIGS. 1 and 2 is an integral type power steering main body 1 that has been widely known in the past in power steering devices. As shown in FIG. 2, the power steering main body 1 is provided with an input shaft (stub shaft) 2 connected to a steering shaft (both not shown) from the steering handle. And a power cylinder 3 for turning the right steering wheel via a steering link mechanism (not shown). In this embodiment, a case of a ball screw type power steering will be described.
[0022]
In FIG. 2, reference numeral 4 denotes a sector gear which is an output shaft of the power cylinder 3. Although not shown, the rotation of the sector gear 4 is a left / right steering wheel provided at the front of the vehicle body from the pitman arm via a drag link and knuckle arm. It is transmitted to a wheel (not shown), and this steered wheel is steered according to the steering operation.
[0023]
1 and 3, reference numeral P1 is an engine-driven main pump driven by a vehicle engine (not shown), and P2 is a drive source other than the engine, for example, a sub-pump driven by rotation of an axle or rotation of an electric motor. Thus, these pumps P1 and P2 draw fluid (hydraulic oil) from the tanks T1 and T2 and discharge them with a required fluid pressure. Fluid pressure (hydraulic pressure) from these pumps P1 and P2 is fed to a flow path switching control valve 10 provided in the main body 1 via a main and sub switching spool valve 20 described later.
[0024]
As shown in FIG. 2, a mechanism part that has been widely known as a ball screw type power steering is formed in the steering body 1. Referring to FIG. 2, reference numerals 5 and 6 denote valve housings that also serve as a steering body that constitutes the above-described steering body 1 and a valve cover that closes the opening end side thereof. A piston 7 having rack teeth that move forward and backward in the axial direction in accordance with the steering operation of a steering handle (not shown) and mesh with the sector gear 4 is disposed in the internal space formed by these. Two pressure chambers (left and right cylinder chambers) 8a and 8b are formed in front of and behind the piston 7, and the left and right cylinder chambers 8a and 8b constitute the power cylinder 3.
[0025]
When the piston 7 is operated, a rack formed on the side of the piston 7 meshes with the sector gear 4 to rotate the axis of the sector gear 4. This rotation is transmitted to the steered wheel side through a pitman arm (not shown) that constitutes the steering mechanism, thereby performing steering.
[0026]
A stub shaft 2 that rotates by a steering operation of the steering handle is penetrated and supported in the valve housing 6, and one end of the stub shaft 2 faces the piston 7 and is connected via a ball screw mechanism 9. A worm shaft 11 is disposed coaxially. Reference numeral 12 denotes a torsion bar which is coaxially disposed in the shafts 2 and 11 and whose both ends are integrally coupled to the shafts 2 and 11 side. In addition, a rotary control valve 10 is provided which operates by rotating the stub shaft 2 and the worm shaft 11 relative to each other by a tension bar 12.
[0027]
The control valve 10 is provided so as to rotate integrally with the inner end of the stub shaft 2 and has a rotor 13 having a plurality of valve grooves on the outer periphery thereof, and is provided integrally with the worm shaft 11 on the inner periphery thereof. And a sleeve 14 having a plurality of valve grooves. The control valve 10 is operated by the relative rotation of the rotor 13 and the sleeve 14 to switch the hydraulic flow path, and the pressure oil from the pump P1 or P2 is supplied to the power by the steering operation of the steering handle. The piston 7 that selectively supplies the left and right chambers 8a and 8b of the cylinder 3 and applies steering assist force to the steered wheels is moved in the steering direction.
[0028]
The specific structure and operating state of the rotary control valve 10 described above, the movement of the piston 7 during steering, and the movement of the sector gear 4 by this movement causes the steered wheels to steer in the required direction. Is widely known, and detailed description thereof is omitted here.
[0029]
According to the present invention, in the power steering apparatus having the above-described structure, the main pump P1 driven by the engine of the vehicle, the sub pump P2 driven by driving means other than the engine, and the steering operation to the steering handle. A control valve 10 for switching the flow path of the pressure fluid from each of the pumps P1 and P2 and a power cylinder 3 for turning the steered wheels by a steering assist force obtained by the pressure fluid switched by the control valve 10 are provided. .
[0030]
A main / sub switching spool valve 20 is provided in the middle of the fluid pressure passage from the main pump P1 and the sub pump P2 to the control valve 10. As shown in FIGS. 1 and 2, the spool valve 20 is provided inside a valve body 21 fixed to a part of the valve housing 6 constituting the power steering main body 1 with a bolt or the like.
[0031]
A part of the valve body 21 is provided with first and second pump ports 22 and 23 to which the main pump P1 and the sub pump P2 are connected, and reflux is performed through the control valve 10 and the spool valve 20. Return ports 24 and 25 are provided for returning the returning pressure oil to the main tank T1 and the sub tank T2.
[0032]
Here, in this embodiment, the valve body 21 including the spool valve 20 described above is integrally provided on the side of the valve housing 6 of the power steering main body 1 of the power steering apparatus, and the space This is advantageous in reducing the overall size and size of the apparatus. Further, in the structure integrally assembled to the steering body 1 in this way, the passages (26, 27) in the body 21 and the passages (16, 17) in the valve housing 6 can be directly connected. This is more practical than the pipe connection and has the advantage of increasing the reliability of the fail mechanism.
[0033]
1 and 2, reference numerals 26 and 27 denote passages formed so as to open to the joint surface of the valve body 21 to the valve housing 6, and these supply pressure fluid from the pumps P <b> 1 and P <b> 2 to the control valve 10. It consists of a passage 26 for sending and a return-side passage 27 for returning the return oil from the control valve 10 to the tanks T1 and T2. In FIG. 1, reference numerals 16 and 17 denote passage holes serving as a P port and a T port of the control valve 10 formed on the valve housing 6 side to which the passages 26 and 27 are connected, and reference numerals 26a and 27a denote sealing O-rings.
[0034]
When such a structure is adopted, the switching spool valve 20 for switching between the main pump P1 and the sub pump P2 is connected to the P port and T port from the flow path switching control valve 10 in the power steering body 1 of the power steering apparatus. Since it can be directly attached to the passage holes 16 and 17 without using connection pipes, the number of parts of the entire apparatus is small, it can be easily assembled, and it can be constructed without a mounting space. There is no leakage problem.
[0035]
As shown in FIGS. 1 and 2, the main and sub switching spool valve 20 includes a spool 32 that is held in a valve hole 31 formed in the valve body 21 so as to be movable in the axial direction. Reference numeral 33 denotes a plug that closes the open end of the valve hole 31, and reference numeral 34 denotes a compression coil spring as urging means that urges the spool 32 to the initial position (right end side in FIG. 1).
[0036]
In the spool valve 20, a pilot passage 36 branched from a part of the first pump port 22 connected to the main pump P1 is connected to the chamber 35 on the right end side, and the fluid of the pressure fluid from the main pump P1. Pressure is introduced as pilot pressure. On the other hand, the chamber 37 on the left end side of the spool valve 20 is connected to the first or second tank port 24, 25 via a passage 38 formed in the spool 32, and becomes a tank pressure. The chamber 37 is connected to the main tank T1 or the sub tank T2 through the passage 38 in accordance with the movement of the spool 32, and is always at a tank pressure.
[0037]
Therefore, the spool 32 is in the state shown in FIG. 1 or FIG. 4 in a state where a fluid pressure higher than a predetermined pressure is supplied from the main pump P1. On the other hand, when the fluid pressure decreases, the spool 32 gradually moves to the right in FIG. 1, and when the fluid pressure is no longer supplied, the urging force of the compression coil spring 34 as shown in FIGS. 5 (the state moved to the right end side in the figure).
[0038]
In the figure, reference numerals 42, 43, 44, 45 are formed on the inner peripheral wall of the valve hole 31 so as to be displaced in the axial direction, and the first and second pump ports 22, 23, the first and second tank ports 24, 25, the annular groove 46, 47 is opposed to the opening end to the valve hole 31 of the passages 26, 27 connected to the passage holes 16, 17 serving as the pump port and tank port of the control valve 10. An annular groove formed on the outer periphery of the spool 32.
[0039]
48 and 49 are two annular grooves formed on the outer periphery of the spool 32. These annular grooves 48 and 49 are formed in the second pump port 23 when the spool 32 is in the state shown in FIGS. It is formed at a position communicating with the corresponding annular groove 43 and the annular groove 45 corresponding to the second tank port 25. These annular grooves 48 and 49 are connected by a short-circuit passage 50 formed inside the spool 32.
[0040]
In such a structure, the spool valve 20 operates as shown in FIGS. 1 and 3 (specifically, FIGS. 4 and 5), and the pressure fluid from the main pump P1 and the sub pump P2 is passed through the control valve 10. Thus, by appropriately feeding the power cylinder 3 and returning the return fluid to the main pump T1 and the sub tank T2 as appropriate, a necessary supply amount can be secured by the power cylinder 3 and an appropriate steering assist force can always be obtained. It is configured as follows.
[0041]
This will be described in detail with reference to FIG. 1, FIG. 2, FIG. 4 and FIG. 5. The spool valve 20 that switches the supply system from the main pump P1 and the sub pump P2 starts the main pump P1 and starts the supply of pressure fluid. At this point, the state shown in FIGS. At this time, depending on the position of the spool 32, the pressure fluid from the main pump P1 is sent from the annular groove 42 through the annular groove 46 to the control valve 10 side through the supply-side passage 26. On the other hand, the return-side passage 27 is connected from the annular groove 47 to the main tank T1 through the annular groove 44, and a return-side flow path is secured.
[0042]
At this time, the sub pump P2 reaches the annular groove 45 from the annular groove 43 via the annular groove 48 on the spool 32 side, the short circuit passage 50, and the annular groove 49, and is connected to the sub tank T2, and is in a so-called short circuit state. . Therefore, the sub pump P2 is operated in a no-load state.
[0043]
In the spool valve 20 described above, as shown in FIG. 4 and the like, the communication portion between the annular groove 43 on the sub pump P2 side and the annular groove 48 on the short circuit passage 50 side is A, and the annular groove 43 on the sub pump P2 side and the pump groove P side are on the pump port P side. The communicating portion with the annular groove 46 is B, the communicating portion between the annular groove 42 on the main pump P1 side and the annular groove 46 on the pump port P side is C, and the annular groove 45 on the sub tank T2 side and the annular groove on the short-circuit passage 50 side are provided. 49, D is a communication portion between the sub-tank T2 side annular groove 45 and the tank port T side annular groove 47, and the main tank T1 side annular groove 44 and the tank port T side annular groove 47. Assuming that the communication portion is F, the open / closed states at A to F have the relationship shown in Table 1 as the spool 32 moves.
[0044]
[Table 1]

[0045]
Here, in Table 1, “closed” is indicated by “x”.
Also, in each of the operating states (1) to (6), an important portion of the states in the communication portions A to F that ensure or block the flow of the pressure fluid is shown in bold.
[0046]
As can be seen from (1) of Table 1 and FIG. 4, when the main pump P1 is normally driven and discharges the pressure fluid, the spool valve 20 has the communication portions A, C, D, and F. Open and closed otherwise.
Therefore, in this state, the pressure fluid is supplied from the main pump P1 and the return side is returned to the main tank T1, and the power cylinder 3 is appropriately operated by the control valve 10 in accordance with the operation of the steering handle. Thus, the steering assist force in a required state can be obtained. In addition, at this time, the communication parts A and D are open in FIG. 4, and the sub pump P2 and the sub tank T2 are short-circuited and are in a no-load state, so that power loss is reduced.
[0047]
In the normal state described above, when the flow rate of the pressure fluid from the main pump P1 decreases and the pilot pressure acting on the chamber 35 decreases, the spool 32 changes from the state of FIG. 4 to the state of FIG. Move to the right.
Explaining these states based on (2) to (4) in Table 1, the supply from the main pump P1 through the communication part C decreases, and the communication part B gradually opens and the pressure from the sub pump P2 is reduced. Fluid supply is started. The state (2) described above is instantaneous, and immediately after (1) to (2), the state (3) immediately follows.
[0048]
At this time, the main pump P1 is switched to the sub-pump P2 including the time when the pressure fluids from the two pumps P1 and P2 flow together.
In this state, the short circuit state between the sub pump P2 and the sub tank T2 is released by gradually closing the communication portions A and D.
[0049]
Further, as shown in (4) to (6) in Table 1, the return fluid from the power cylinder 3 passes through the return path from the return path to the main tank T1 to the two tanks T1 and T2, and then passes through the sub tank T2. It will switch to the return path to.
[0050]
Even on such a return side, since switching between the main and the sub is performed after passing through the return state to both tanks T1 and T2, the flow amount on the return side can be ensured sufficiently and sufficiently, so that the power cylinder 3 It will not interfere with the operation on the side.
Here, the state {circle around (5)} described above is for securing a return-side flow path in the process of closing the communication path F, and the switching from (4) to (6) is also instantaneously performed.
3 and FIG. 5, the supply path on the main pump P1 side and the return path to the main tank T1 are completely closed, and the supply path from the sub pump P2 and the return path to the sub tank T2 are separated. It is secured.
[0051]
In the spool valve 20 that switches the main and sub pumps P1 and P2 of the power steering apparatus 1 as described above, when the fluid pressure of the pressure fluid on the main pump P1 side is operated as a pilot pressure, The main and sub pumps are not simply switched with the movement, but the main pump P1 and the sub pump P2 and the main tank T1 and the sub tank T2 are simultaneously connected to the pump port P and the tank port T of the control valve 10 respectively during the switching. Is provided. Therefore, the supply amount and return amount of the pressure fluid during the switching of the spool valve 20 are not insufficient, and the required supply amount between the pumps P1, P2, tanks T1, T2 and the power cylinder 3 is By obtaining the return amount, the steering assist force by the power cylinder 3 can be appropriately generated.
[0052]
In other words, according to the present invention, by using the switching spool valve 20 described above, any cylinder chamber of the power cylinder 3 is normally supplied via the control valve 10 by the supply of the pressure fluid from the main pump P1. Pressure fluid is supplied to 8a and 8b, and the other chamber is connected to the main tank T1, and a steering operation can be easily performed by obtaining a required steering assist force.
In the unlikely event that the flow rate of the pressurized fluid from the main pump P1 decreases, the switching spool valve 20 is actuated by the decrease in the pilot pressure to switch between the feeding system and the reflux system, and from the sub pump P2. Steering can be easily performed by the pressure fluid.
[0053]
Note that the present invention is not limited to the structure described in the above-described embodiment, and it goes without saying that the shape and structure of each part can be appropriately modified and changed.
For example, a pump driven by an automobile engine is used as a hydraulic source for operating a power steering main body 1 of a power steering device for turning a steered wheel, and a main pump P1 is used as an auxiliary hydraulic source. Although the case where the sub-pump P2 is used as the pump driven by the rotation of the axle or the electric motor has been described, the present invention is not limited to this. For example, both the main pump P1 and the sub pump P2 may be driven by an electric motor.
[0054]
Of course, the sub-pump P2 is not limited to the above-described axle drive system or an electric drive type using an electric motor, but may be any pump that can be driven by an appropriate drive source other than the engine.
In the above-described embodiment, the case where the main tank T1 and the sub tank T2 are separately provided on the return side of the pressure fluid has been described. However, these may be configured by a common tank.
[0055]
In the above-described embodiment, the case where the power steering main body 1 is a ball screw type has been described. However, the present invention is not limited to this, and the power steering main body 1 is of a rack and pinion type or other types of power steering structures. Also good.
[0056]
【The invention's effect】
As described above, according to the power steering apparatus of the present invention, only the main pump is always connected to the control valve by the main and sub switching spool valve, and the pressure fluid from the main pump is used for switching the flow path. The power can be fed to the power cylinder via the control valve to generate a required steering assist force, so that the steered wheel can be steered in a required state accompanying the steering operation of the steering handle. In addition, at this time, since the sub pump is connected to the tank side and is operated in a no-load state, no power loss occurs.
[0057]
Further, according to the present invention, unlike the conventional apparatus, the pressure fluid from the main pump is not supplied via the throttle portion, and the pressure fluid from the sub pump is not supplied via the check valve. The presence of the switching valve does not cause power loss.
[0058]
Further, according to the present invention, for example, when an engine-driven main pump fails or a pressure fluid supply pipe from the pump is damaged, a spool that uses the pressure fluid of the main pump as a pilot pressure. The valve is switched instantaneously, the sub pump is connected to the control valve, and the pressure fluid from this sub pump can be fed to the power cylinder through the control valve, so the left and right steering wheels are steered with the required steering assist force. can do.
[0059]
Therefore, according to the present invention, the two pumps, main and sub, and the spool valve for switching the feeding system, stop the engine-driven pump of the vehicle due to a failure or the like, and supply piping for the pressure fluid from the pump Even if it is damaged, the left and right steering wheels can be steered, and the number of components of the device is small, the structure is simple, and the size and cost reduction are wasteful despite the device structure. There is no consumption horsepower, and fuel consumption can be improved by reducing the flow rate.
[0060]
Further, according to the present invention, when the spool valve is switched, for example, when switching from the main pump to the sub pump, the pressure fluid from both the main pump and the sub pump is supplied to the control valve through the state of supplying the pressure fluid from both the main pump and the sub pump. It is equipped with a flow path that switches the flow path that feeds to the sub tank and returns the fluid returned from the control valve to both the main tank and the sub tank. Thus, the flow rate of the pressure fluid to the power cylinder and the flow path of the return side fluid are always ensured sufficiently and the steered wheels can be steered in a required state.
[Brief description of the drawings]
FIG. 1 shows an embodiment of a power steering apparatus according to the present invention, and is an end view of a power steering main body section in which a switching spool valve portion as a main part is cut.
FIG. 2 is a side sectional view of a power steering main body in FIG.
3 is an end view of the power steering main body showing a state in which the switching spool valve of FIG. 1 is switched from the main side to the sub side.
4 is an enlarged cross-sectional view of a switching spool valve that is a main part of FIG. 1. FIG.
5 is a cross-sectional view when the spool valve is switched from the state of FIG. 4 to a state corresponding to FIG. 3 described above.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Power steering main-body part of a power steering device, 2 ... Input shaft (stub shaft), 3 ... Power cylinder, 4 ... Output shaft (sector gear), 5 ... Steering body, 6 ... Valve housing, 7 ... Piston, 8a, 8b: Left, right cylinder chamber, 10 ... Control valve for switching the flow path, 11 ... Worm shaft, 13 ... Rotor, 14 ... Sleeve, 16, 17 ... Passage, 20 ... Spool valve for main and sub switching, 21 ... Valve body , 22, 23 ... first and second pump ports, 24, 25 ... first and second return ports, 26, 27 ... passage, 31 ... valve hole, 32 ... spool, 33 ... plug, 34 ... compression coil Spring (biasing means), 35 ... chamber, 36 ... pilot passage, 37 ... chamber, 38 ... passage, 50 ... short circuit passage, P1 ... main pump, P2 ... sub pump, T1 Main tank, T2 ... the sub-tank.

Claims (5)

A main pump and a sub pump;
A power cylinder that steers the steering wheel by steering steering of the steering handle;
A control valve for switching a flow path, which is supplied with pressure fluid from each of the pumps and selectively supplies the power cylinder;
A main tank and a sub tank for storing hydraulic oil;
A main and sub-switching spool valve that selectively switches the flow path by the pressure fluid supplied from the main pump;
A pump that connects the flow path switching control valve and a main / sub switching spool valve and supplies pressure fluid from the main pump and sub pump to the flow path switching control valve from the main / sub switching spool valve. Port,
The flow path switching control valve is connected to the main and sub switching spool valves, and the return oil returned to the main tank and sub tank is returned from the flow path switching control valve to the main and sub switching spool valves. Tank port
With
The main / sub switching spool valve has a first position in which pressure fluid from the main pump is supplied to the power cylinder and pressure fluid from the sub pump is returned to the sub tank, and pressure from the sub pump. Operating between a second position where only fluid is supplied to the power cylinder;
The power steering apparatus, wherein the main pump and the sub pump simultaneously communicate with the pump port during the switching from the first position to the second position.  The power steering apparatus according to claim 1, wherein a pilot pressure passage having a pressure fluid supplied from the main pump as a pilot pressure is connected to one end of a spool constituting the spool valve, and the spool is connected to the other end. A power steering apparatus comprising a biasing means for biasing at one end side.  3. The power steering apparatus according to claim 1, wherein the spool constituting the spool valve is provided with a short-circuit passage that connects the sub-pump to the sub-tank during a normal operation to make a short-circuit state. Power steering device to do.  3. The power steering apparatus according to claim 1, wherein pressure fluid from the main pump is supplied to the control valve during normal operation to a spool constituting the spool valve, and pressure from the main pump is increased. When the flow rate of the fluid decreases, the flow path for switching the flow path for supplying the pressure fluid from the sub-pump to the control valve and the return fluid from the control valve during normal operation are returned to the main tank, A power steering apparatus comprising: a flow path for switching a flow path for returning to the sub tank when the flow rate of the pressure fluid from the main pump decreases. In the power steering apparatus according to claim 1,
The main / sub switching spool valve has a state in which the main tank and the sub tank communicate with the tank port at the same time during switching from the first position to the second position. Power steering device.

Images